In the construction industry, it is difficult to determine distant horizontal or vertical lines on the walls by a reference line, especially to draw desired lines at different walls. Conventional methods for carrying out the line-drawing or line-determination operation can be performed by utilizing rulers, ink-string boxes, levelers as are well-known in the art. However, the conventional methods may be tedious and difficult to achieve accuracy at operation, and man-made errors occur.
The datum horizontal indication performed by the level includes the type of beam-directed or beam-rotated emission in the prior art. The beam-directed emission diffuses the laser beam to profile a line-shaped using a cylindrical lens along a horizontal direction so that the laser beam is projected on the surface of the desired object. The disadvantage of the beam-directed emission is that the emission angle of the light beam is severely restricted within a small range after the laser beam is sent out. In other words, the length of the line-shaped is decreased. For the indication of a longer datum line or circular plane with 360 degrees on the objects in a specific application, it is necessary to perform many indication steps or combine a plurality of lenses. As a result, the above-mentioned method is not easy to be operated and subject to a complex assembly of the lenses.
In the type of beam-rotated emission, a dot-shaped emitted by laser facula forms a horizontal fan covering at a high-speed rotation. Due to the persistance of vision, the dot-shaped profile is projected on the distant vertical plane to generate a line of the laser facula. The disadvantage is that the vibration of the structure of the beam-rotated emission degrades the precision of the level due to rotation of the beam. Additionally, the power consumption of the rotational mechanism may increase the manufacturing cost and the size of the level.
For another type of level in the prior art, a laser level is composed of four identical optical systems implemented by the beam-directed emission. Each optical system is disposed to form an included angle with 90 degrees in a horizontal plane. Each optical system includes a laser diode, a regular lens and a cylindrical lens. The beam of light is generated from the laser diode and delivered through the regular and the cylindrical lens to form a light emission having a diffusion angle greater than 90 degrees in the horizontal plane. By adjusting the position and the inclination angle of each optical system, all the light emissions are integrated into a light beam with 360 degrees. However, such a structure uses four laser diodes and the four set of optical systems results in increment of manufacturing cost. Further, it is necessary to carefully calibrate the optical systems and the assembly difficulty and complexity of the level will considerably decrease the production efficiency.
In addition, U.S. patent application Ser. No. 10/838,348 discloses a laser level filed on May 5, 2004. The laser level utilizes two optical systems with beam-directed emission to form a beam-split element and the two optical systems are disposed at a position of 180 degrees in a horizontal plane. Each of the optical systems comprises a laser diode, beam-split element two sets of regular and cylindrical lens which are perpendicular to each other. The light beam emitted from the laser diode is delivered through the beam-split element, regular lens and the cylindrical lens to form two perpendicular light emissions having a diffusion angle greater than 90 degrees in the horizontal plane. By adjusting the position and the inclination angle of each optical system, all the light emissions are integrated into a light beam with 360 degrees. However, although the level has two optical systems, four sets of regular lenses and cylindrical lenses are installed in the laser level, thereby resulting in high manufacturing cost and complex assembly, which is disadvantageous to the production efficiency of the level.
Consequently, there is a need to develop a laser level to transfer the light emitted from a laser diode into a circular plane with 360 degrees to reduce the manufacturing cost and the size of the laser level.